At 7:59 p.m. on Aug. 4, thousands of feet above one of the world's most rugged borders, a Pakistani air force F-16 fighter plane opened fire on a Soviet SU-25 fighter-bomber that had penetrated Pakistani airspace. The encounter was brief: A single missile from the F-16 scored a direct hit. The Soviet plane, which Pakistan alleges was carrying cluster bombs meant for Pakistani villagers, crashed 15 miles inside Pakistan. The pilot, Col. Alexander V.

In his first visit here since he assumed power, Afghanistan's interim prime minister, Hamid Karzai, pledged to work for the release of "good" Pakistanis captured alongside Taliban troops and asked Pakistan to continue supporting Afghan refugees until his nation is ready for their return. The neighboring countries also vowed to rejuvenate "strong brotherly relations" based on mutual respect and trust.

President Reagan pledged Wednesday that U.S. military aid for Pakistan will continue undiminished despite the death in a plane crash of autocratic President Zia ul-Haq, but American foreign policy experts said a period of instability that could damage U.S. policy from Afghanistan to the Persian Gulf is almost a certainty.

A dispute over blockades hemming in thousands of malnourished Afghans broke down peace talks Sunday that had come tantalizingly close to ending two decades of bitter conflict. "They have been suspended indefinitely," said James Ngobe, the United Nations representative at the troubled talks. The Taliban militia, which wants a ruling government of Islamic scholars in place before the blockades are lifted, accused U.N.

Pakistan's air force shot down an Afghan combat plane that had penetrated six miles into Pakistani territory, the Defense Ministry said in Islamabad. A ministry statement said debris from the aircraft was seen falling in the mountains north of Miranshah on the northwest Pakistan border. It was the second intruding Afghan plane brought down by Pakistan in four weeks.

Afghanistan's warring factions promised Sunday to continue a cease-fire as they opened face-to-face talks in Pakistan aimed at ending the bloody civil war that is devastating their impoverished nation. The battlefield, just 18 miles north of Afghanistan's capital, Kabul, was silent as a reading from the Muslim holy book, the Koran, marked the ceremonial opening in Islamabad, the Pakistani capital, of the two sides' first direct talks.

A dispute over blockades hemming in thousands of malnourished Afghans broke down peace talks Sunday that had come tantalizingly close to ending two decades of bitter conflict. "They have been suspended indefinitely," said James Ngobe, the United Nations representative at the troubled talks. The Taliban militia, which wants a ruling government of Islamic scholars in place before the blockades are lifted, accused U.N.

President Zia ul-Haq touched off a verbal exchange with the Kremlin on Saturday when he said that the Soviet Union had decided to halt its military withdrawal from Afghanistan and had brought 10,000 troops back into Kabul, the Afghan capital, to bolster the city. In Moscow soon afterward, Marshal Sergei F. Akhromeyev, chief of staff of the Soviet armed forces, flatly denied the report and described the Pakistani president's statement as "pure slander."

Afghan jets bombed a remote Pakistani border village at night last week, killing 27 people and wounding 25, a government statement said. The attack on the village of Baghar, in the South Waziristan tribal area, was the most serious reported by Pakistan since the signing in April of U.N.-mediated accords under which the Soviet Union began withdrawing its more than 100,000 troops from Afghanistan on May 15.

Afghan negotiators Thursday announced a plan for accelerated withdrawal of Soviet troops from Afghanistan, a development that removes one of the last obstacles to agreement on restoring peace in the war-torn country. Abdul Wakil, the foreign minister of Moscow's client regime in Kabul, the Afghan capital, disclosed that the proposed timetable for the Soviet pullout had been shortened from 10 months to 9 and that half of the estimated 115,000 troops would leave in the first three months.

Afghanistan's warring factions promised Sunday to continue a cease-fire as they opened face-to-face talks in Pakistan aimed at ending the bloody civil war that is devastating their impoverished nation. The battlefield, just 18 miles north of Afghanistan's capital, Kabul, was silent as a reading from the Muslim holy book, the Koran, marked the ceremonial opening in Islamabad, the Pakistani capital, of the two sides' first direct talks.

The Taliban militia, now the uncontested masters of Afghanistan's capital, chased the soldiers of ousted President Burhanuddin Rabbani north of Kabul on Friday and began putting in effect its version of strict Islamic rule. Women were barred from offices until further notice and told to wear traditional Islamic veils when outside the home, reports reaching this city near the Afghan-Pakistan border said.

Army commandos stormed the Afghan Embassy late Monday, freeing five schoolboys and a teacher and killing three masked Afghan gunmen who had held them hostage for nearly 40 hours. The kidnapers "had every intention of shooting us, but they . . . were killed before they could move," one of the boys told state-run TV.

Three Afghans armed with pistols and hand grenades hijacked a school bus to Islamabad from the northwestern Pakistani town of Peshawar on Sunday, taking 73 schoolchildren and staff hostage, officials and witnesses said. The masked gunmen, who later released all but 16 Pakistani schoolboys, said they wanted $5 million, officials said. Earlier, the gunmen said they would free the boys, ages 12 to 14, only after food supplies were delivered to the beleaguered Afghan capital, Kabul.

After waging guerrilla warfare in Afghanistan for 13 years, rebel Commander Syed Hussein Anwari sat beneath an oil painting of his hero, the late Ayatollah Ruhollah Khomeini of Iran, and tried to resign himself to the notion of peace.

Afghanistan's renegade defense minister, Shahnawaz Tanai, declared Thursday that "the fight is not over," but his bloody attempt to overthrow President Najibullah's Soviet-backed government this week has driven deeper divisions into the ranks of the regime's enemies, diplomats and independent analysts said.

Afghanistan and Pakistan traded accusations about prolonging the Afghan civil war as nonaligned diplomats worked on a series of bland statements to paper over their differences on regional conflicts. The dispute between the two nations came at the summit of the 102-nation Nonaligned Movement in Belgrade, Yugoslavia. Pakistan was angered by a speech in which Afghan President Najibullah accused Islamabad of waging war against his government by supplying arms to rebel groups.